Industrial automation systems are used for monitoring, controlling and regulating technical processes, particularly in the field of production, process, and buildings automation. Such systems allow operation of control devices, sensors, machines and industrial installations that are intended to operate as autonomously and independently of human interventions as possible. Due to the ever rising importance of information technology for automation systems (that comprise numerous networked control or computer units), methods for reliably providing functions distributed over an automation system for monitoring, control, and regulatory functions are becoming increasingly important.
For distributed services, the service components that are provided by a plurality of different control or computer units for realizing functions of an automation system, impose great demands on a communication infrastructure of the automation system. Firstly, it may be necessary to meet demands for realtime-compatible communication, having a comparatively large number of relatively short messages. Secondly, different communication protocols may be required to be used as transparently as possible for distributed services. A weak communication infrastructure can compromise error-free provision of a service and have a disadvantageous effect on system stability and availability. Regarding time-critical constraints in technical systems that are automated by industrial automation appliances, realtime communication protocols such as PROFINET, PROFIBUS or Real-Time-Ethernet are typically used for communication between automation appliances in industrial communication networks.
For access to measured values and data associated with services within an industrial automation system, there are often extremely different client demands in terms of availability or quality of service and also in terms of data filtering or information pre-compression. In addition, there are demands for extendibility of existing services by virtue of optional or additional service components without the need to substantially change a data and function model on which an implementation of an existing service is based.
WO 2004/109415 A1 discloses the practice of providing functions of an industrial automation system by means of services and of dividing function blocks into standard functions blocks and flexible function blocks. In this reference, input and output parameters of function blocks comprise a value field and a status field, which in turn has quality, substatus and limit-value attributes. To aid configuration, an interface device is provided.
US 2004/230643 A1 describes a method for providing services in a system comprising a plurality of computer units that involves services being made available by means of enterprise application integration. In this reference, services are called using a standard find-bind-execute mechanism. Furthermore, TCP/IP packets that can combine results of logically coherent operations are transmitted between a client and a server. By way of example, a result element can be combined in a TCP/IP packet in advance if, in terms of its useful data, the result is too large for a TCP/IP packet.
WO 2008/090216 A1 discloses an automation system having a service-oriented architecture and local, distributed components or appliances in a flexible and reconfigurable production environment, having at least one host computer that is connected to the service-oriented components or appliances by means of a data transmission means such as Ethernet.
General aspects of service-oriented architectures (SOA) in connection with the use of standardized communication protocols are described in F. James et al., “SERVICE-ORIENTED PARADIGMS IN INDUSTRIAL AUTOMATION”, IEEE Transactions on Industrial Informatics, vol. 1, No. 1, February 2005, ISSN 1551-3203, pages 62-70. F. Mustafa et al., “DYNAMIC WEB SERVICE COMPOSITION”, 2009 International Conference on Computer Engineering and Technology, ICCET 2009, 22 Jan. 2009, ISBN 978-1-4244-3334-6, pages 463-467 cite Quality of Service (QoS) as a problem area within the context of service-oriented architectures. However, this reference does not deal with division of service components into service-specific and non-service-specific components.
US 2004/221005 A1 discloses that services may comprise service-specific and non-service-specific components. However, this reference does not state that QoS measurements can be safeguarded by non-service-specific components.
EP 2 141 562 A1 discloses that distributed services in an automation system, comprising a plurality of networked computer units, are provided within a service-oriented architecture. A service-requesting computer unit divides service requests on the basis of service-providing computer units and transmits them thereto for processing. A service-providing computer unit divides the received service requests into operations that deliver logically coherent result elements. The service-providing computer unit transmits a message containing the logically coherent result elements to the service-requesting computer unit as early as when logically coherent result elements associated with an operation of a service request are available.
EP 2 221 682 A1 describes a method for providing functions in an industrial automation system that involves functions of the automation system being made available by services. Components of a service are split into service-specific components and into components that can be reused by a plurality of different services. Service-specific components and reusable components have a standard configuration interface. Service components are linked via a service configuration unit to form a service via the standard configuration interface. Functions for monitoring or controlling a defined quality of service are assigned to the reusable components.
According to EP 2 224 297 A1, components of a service are linked by a local service configuration unit to form a service via a standard configuration interface in order to consistently provide configuration data in an industrial automation system. Services are configured and activated by configuration data, the configuration data comprising information concerning the assignment of services to control units and concerning dependencies between services. The configuration data are adopted by a system configuration service from a control and monitoring unit of the automation system, checked, and transmitted to one or more destination control units. The transmitted configuration data are checked for changes in comparison with previously used configuration data by local service configuration units associated with the destination control units. The local service configuration units use changes that are established in the configuration data to ascertain lists of operations for making configuration changes, the lists being optimized to minimize service down times.